My engine is the 5. 9L with a 6 speed manual. I am having problems with the engine stumbling. It feels like you hit a puddle of water. I have not noticed the RPMs dropping. The fuel filter has been changed three times since Oct 09. The first time it was really dirty. The lift pump has been changed also. All of this has been brought about from an accident from a tree that fell into the road on a curve. I ran over the top of the tree. I think this stirred up the sediment in the tank. Am I going to have to change the injectors? No codes have been generated.